An intaglio printing press and mobile carriage of the above-mentioned types are disclosed in International Application No. WO 03/047862 A1 (which corresponds to U.S. Pat. No. 7,011,020 B2 in the name of the present Applicant) which intaglio printing press is reproduced in FIGS. 1A and 1B hereof. The intaglio printing press disclosed in this document comprises a first mobile carriage 11 supporting the ink-collecting cylinder 12 (also referred to as “Orlof cylinder”), as well as four colour-selector cylinders 13 (also referred to as “chablon cylinders”) and a second mobile carriage 14 supporting four inking units 16 associated to the colour-selector cylinders 13. On the other hand, the plate cylinder 07 (or “intaglio printing cylinder”) and the impression cylinder 06 (with its sheet grippers 08) are supported in a stationary machine frame 01 of the press. According to International Application No. WO 03/047862 A1, the two mobile carriages 11, 14 are suspended under suspension rails 04 below the endless chain gripper system 09 that takes the printed sheets away from the impression cylinder 06 so as to free the floor 02 onto which the printing press is installed from any supporting rails, the suspension rails 04 being supported at one end by the stationary machine frame 01 and at the other end by a supporting upright 03. The axes of rotation of the ink-collecting cylinder 12 and of the plate cylinder 07 are located in the same horizontal plane and movement of the mobile carriages 11, 14 takes place along this horizontal plane. As illustrated in FIG. 1A, thanks to this arrangement, a working space 17 big enough for a human operator can be formed between the first and second mobile carriages 11, 14 by moving the second mobile carriage 14 away from the first mobile carriage 11. As shown in FIG. 1B, a similarly big working space 18 can be formed between the first mobile carriage 11 and the stationary machine frame 01 by further moving the first mobile carriage 11 away from the stationary machine frame 01.
Swiss Patent No. CH 685 380 A5 and European Patent Application No. EP 0 563 007 A1 (which corresponds to U.S. Pat. No. 5,282,417) also disclose an intaglio printing press with first and second mobile carriages. In contrast to the previously-mentioned intaglio printing press, the first mobile carriage exclusively supports the ink-collecting cylinder, the colour-selector cylinders being located in the second mobile carriage together with the associated inking units. This is necessitated by the fact that, according to Swiss Patent No. CH 685 380 A5 and European Patent Application No. EP 0 563 007 A1, the ink-collecting cylinder is adapted to be removed from the press so as to convert the intaglio printing press from a press with indirect inking system to a press with direct inking system, and vice versa. The axes of rotation of the ink-collecting cylinder and of the intaglio printing cylinder are still located in the same horizontal plane and movement of the mobile carriages also takes place along this horizontal plane.
It has become apparent that the location of the ink-collecting cylinder in a mobile carriage could be problematic in that one loses the necessary circumferential register between the ink-collecting cylinder and intaglio printing cylinder as a result of rotating the ink-collecting cylinder during maintenance operations. Indeed, perfect circumferential register between the ink-collecting cylinder and the intaglio printing cylinder is critical in that this circumferential register determines the preciseness of the inking on the intaglio printing cylinder and therefore affects the printing quality.
In addition, as disclosed in International Application No. WO 03/047862 A1, Swiss Patent No. CH 685 380 A5, and European Patent Application No. EP 0 563 007 A1, it had previously been considered necessary to ensure that the axes of rotation the ink-collecting cylinder and of the intaglio printing cylinder should be aligned with the direction of displacement of the mobile carriage supporting the ink-collecting cylinder (i.e. in a horizontal plane) so as to avoid as much as possible occurrence of such circumferential register issues upon separation or joining of the ink-collecting cylinder and of the intaglio printing cylinder. Such horizontal arrangement of the ink-collecting cylinder and of the intaglio printing cylinder however has a negative effect on the machine footprint.
There is therefore a need for an improved intaglio printing press of the above-mentioned type where the ink-collecting cylinder is supported in a mobile carriage.